The present invention relates generally to control systems for position sensing, and more specifically, to detecting faults in linear variable differential transformers and rotary variable differential transformers.
Position sensors are utilized in many different applications, including in gas turbine engines for aeronautical, marine, and industrial applications. Such engines often include, for example, rotary voltage differential transducers (RVDTs) and linear voltage differential transducers (LVDTs). The transducers are coupled to actuators, and provide a voltage signal proportional to a stroke position of the actuator.
To detect faults in RVDTs and LVDTs, a range test can be performed on the sum of secondary voltages from the transducers. A range test also can be performed on a sensed position to verify signal integrity. The range limits, however, must be set wide enough to account for all worse-case system variations. Otherwise, a properly operating transducer may be identified as having a fault. These wide range limits result, however, in detecting only extreme faults due to electrical open circuits or short circuits. Failures which cause only minor shifts in the sensed position value may not necessarily be detected, even though such failures can impact control system operation.